After Savage, Domning & Thewissen, 1994, Domning, Beatty, Portell, Donovan, Mitchell, MacPhee & Flemming, 2001, and Domning, 1996, 2001

<==o Sirenia Illiger, 1811 (seacows, dudongs and manatees; seireenieläimet)
   |?- †Ishatherium subathuensis
   |--o Prorastomidae Cope, 1889 [Prorastomatidae Flower & Lydekker, 1891; Prorastominae Reinhart, 1959]
   |  |-- †Pezosiren portelli Domning, 2001; M. Eoc. CAm. [was Sirenia genera et species indet. (Domning et al., 2001)]
   |  `-- †Prorastomus sirenoides Owen, 1855 [Prorastoma sirenoides (Owen, 1855) Lydekker, 1895] Eoc. Car. NA.
   `--+--o †Protosiren Abel, 1907 [Protosirenidae Sickenberg, 1934]
      |  |?- ?†P. minima (Desmarest, 1822) Hoojir, 1952
      |  |-- †P. sattaensis
      |  |-- †P. fraasi Abel, 1907
      |  `-- †P. smithae Domning & Gingerich, 1994
      `--+?- †Sirenotherium pirabense Paula Couto, 1967 [Dugongidae or Manatidae incertae sedis]
         |-- Dugongidae Gray, 1821 [Halicoridae; Dudongidae (lapsus calami)] (dugongs, seacows; merilehmät)
         `-- Trichechidae Gill, 1871 [Manatidaespan class="isoa">] (manaatit)

Reference(s):